Sinter grate carriage



June 12, 1962 H. NAGEL ETAL SINTER GRATE CARRIAGE Filed Dec. 19, 1958 by, mm1-Raw@ y 4mm/5 ffy; 5

nited ttes 3,038,712 SINTER GRATE CARRIAGE Horst Nagel and Werner Veith, Frankfurt am Main, Germany, assignors to Metallgesellschaft Aktiengeselln schaft, Frankfurt am Main, Germany Filed Dec. 19, 1958, Ser. No. 781,569 Claims priority, application Germany Jan. 2, 1958 6 Claims. (Cl. 266-21) This invention relates to the construction of a carriage for a sintering apparatus. In particular, the invention is directed to the construction of the grate for the carriage.

The grate bars -for the carriages of a sintering apparatus are supported by` beams and are made of grey cast iron as long as the temperatures inthe sintering beds supported by the grate bars are not so high as to heat the supporting beams above 400 C. For example, this occurs during the sintering of a crumbled iron ore mixture composed exclusively or primarily of hematite ore. In sintering processes which require higher temperatures, the supporting beams for the grate bars must be composed of a high temperature resisting cast alloyed steel, or excessively thick protecting grate layers of inert materials must be used to insulate the grate bars and supporting beams. Such layers must protect the bars and beams from being heated to a temperature above 400 C., but in so doing lessened the output per square meter of sinter bed area. Temperatures above 400 C. will occur, for example, during the sintering of magnetite iron ores or during the most modern burning of cement clinkers. These modern processes are performed at high temperatures on the sintering band because of technical advantages which are achieved, and have forced the use of high-grade cast steel supporting beams instead of the less expensive grey cast iron beams. The difference in cost is a disadvantage as the high-grade cast steel costs from 2 to 2.5 times as much as grey cast iron.

The objects of this invention are to produce a grate carriage construction which permits the use of grey cast iron supporting beams, even if the temperatures employed are raised from 400 to 500. This increase in temperature is suicient to perform most of the processes which would otherwise require the supporting beams to be composed of high-grade cast steel.

In the sintering processes contemplated by this invention, the air or gas is drawn downwardly through the bed of hot sintered material and exhausted through the grate which supports the bed of sinter material. The hot gases intensely heat the grate bars and the supporting beams for the bars.

This invention is based on the discovery that the heat affecting the supporting beams comes not only from radiation and convection of the hot gases, but about from 35 to 40% of the heat is transferred directly by conduction from the grate bars to the supporting beams. This percent of conducted heat is lessened or even eliminated in this invention by including an intermediate insulating member between the contacting surfaces of the grate bars and the supporting beams.

The intermediate member of this invention is shaped to the contour of the supporting beam so that the latter is insulated throughout its surface contact with the grate bars. This insulating intermediate member preferably consists of a material which is not only non-heat conductive, but is also substantially shock proof. Such materials are known in the manufacture of electrical insulators and consist of ceramics, such as porcelain or steatite. It has been unexpectedly found that this insulating intermediate member decreases the flow of heat from the grate bar to the supporting beam, even though the insulating member is composed of a material which has substantially the same heat conductivity as either the grate bar or the 3,038,712 Patented `Furie 1 2, 1,962

supporting beam. Materials useful for the insulating intermediate member are metals having sulcient density without too great a heat conductivity, as, for example, cast iron, cast steel, steel, spherolitic cast iron, and the like.

The means by which the objects of the invention are obtained are disclosed more fully with reference to the accompanying drawings, in which:

FIGURE l is a side elevational View, partly in section, showing the prior art carriage holding a bed of sinter materal;

FIGURE 2 is a similar view showing the construction according to this invention; and

FIG. 3 is a detailed view showing a special embodiment of this invention.

In both FIGURES l and 2, the sintering apparatus has a frame 1 upon which roll wheeled grate carriages 2 holding the bed 3 of sinter material. Each carriage is composed of a frame -upon which the wheels are journalled, including flanged supporting beams 4a (FIGURE l) and 4b (FIGURE 2) which carry the grate bars 5 having bifurcated ends embracing the beam flanges. The space between the bifurcations of each grate bar end is wider than the thickness of a supporting beam flange. In the prior art construction of FIGURE 1, the ends of the grate bars 5 directly contact beams 4a. In FIGURE 2, the supporting beam 4b has an insulating intermediate member 6 applied thereto which separates the surface of beam 4b from grate bar 5. Member 6 extends over the top surface of beam 4b and partially down the side walls of the beam.

When ceramic materials are used for member 6, the amount of heat directly transferred from the sintering bed through the grate bars and onto beam 4b is reduced by about This means that the temperature of the sintering process in bed 3 can be kept, in FIGURE 2, from 70 to 100 C. higher than in FIGURE l as the temperature of supporting beam 4b is not unduly raised thereby.

When member 6 is composed of a material having the same heat conductivity as that of the grate bar or supporting beam, the insulation effect is not as great as in the use of ceramics, but is still considerable. In the most unfavorable case, at least 20% of the heat will be kept from passing to the supporting beam. This unexpected feature appears to be due mainly to the resistance to heat transfer on the large boundary surface.

FIG. 3 shows a detailed view of the insulating member 6 in a special embodiment of this invention. In this case the insulating member 6a does not extend to the side walls of a beam 4b as it is the case in F-IG. 2. Members 6a make it also possible to reduce the heat ow still further when the surfaces of the member 6a contacting the surface facing beam 4b are -Inade irregular by being roughened or formed with ridges, edges, `or the like, which decrease the effective contact area between the surfaces. This construction reduces the heat flow to about half of the value which would occur without member 6a. This enables the construction of an apparatus for very rough or hard operation which would not permit the use of shock-sensitive ceramic materials for the intermediate members, and at the same time achieves a considerable decrease in the ow of heat from the grate bars to the supporting beams by means of metallic members 6a.

The `construction of this invention is not limited solely to the use of grey cast iron supporting beams in processes which would otherwise require beams of cast alloyed steel, but can be used in apparatuses having supporting beams of cast alloyed steel. Consequently, the temperature of the sinter bed can be even more increased with the advantages attendant thereupon.

Having now described the means by which the objects of the invention are obtained.

We claim:

1. In a sinter grate carriage having a wheel supported frame including a plurality Yof flanged supporting beams, grate bars having bifurcated ends loosely embracing the flanges of said beams, the space between the bifurcations of each grate bar being wider than the thickness of an embraced ange, said bars being spaced from each other to form a gas pervious sinter grate, and an insulating member interposed between each bifurcated end and the embraced flange.

2. In a carriage as in claim 1, said insulating member being shaped to the contour of its respective beam.

3. In a carriage as in claim 1, said insulating member being composed of metal.

4. In a carriage as in claim 2, said insulating member being composed of a ceramic material.

5. In a carriage as in claim 3, said insulating member having an irregular surface contact with its respective beam.

6. In a carriage as in claim 3, said insulating member being grey cast iron.

References Cited in the file of this patent UNITED STATES PATENTS 

